Those are just brand names, people use them because they are cheap & easy to get here in the US. If Guns are illegal in your country you're probably not gonna find Birchwood-Casey stuff.
Murphy's Oil Soap is a hardwood floor cleaner.
Old English Lemon Oil is lemon oil.
Birchwood Casey Tru-Oil is a linseed oil based sealer oil.
Birchwood Casey Gunstock Wax is mainly carnauba, they mixed other stuff in it to make it softer. Pure carnauba is too hard to hand wax, you'll need a buffing wheel. (Don't use auto wax even if it says it's carnauba!)
You can get those kind of stuff in any furniture/home improvement/woodworking stores. Probably cheaper...